A photographic process using silver halide is excellent in photographic characteristics such as sensitivity and gradation control as compared with an electrophotographic process and a diazo photographic process. Hence, the photographic process is most widely used. Recently, however, a technique of simply and quickly obtaining images by changing an image forming process of a photographic light-sensitive material using silver halide from a conventional wet process by processing liquids such as developer, etc., to a dry process by heating, etc., has been developed.
Heat developable light-sensitive materials are known in the field of the art and heat developable light-sensitive materials and the processes therefor are described, for example, in Shashin Kogaku no Kiso (Basis of Photographic Industry), pages 553-555 (published by Corona Co., 1979); Eizo Joho (Image Information), page 40 (published April, 1978); Nebletts Handbook of Photography and Reprography, 7th Ed., pages 32-33 (published by Van Nostrand Reinhold Company); U.S. Pat. Nos. 3,152,904, 3,301,678, 3,392,020, 3,457,075, British Pat. Nos. 1,131,108, 1,167,777, and Research Disclosure, pages 9-15 (RD-17029), June, 1978.
For obtaining color images, various processes have been proposed. For example, regarding a process of forming color images by the coupling of the oxidation product of a developing agent and couplers, a combination of a p-phenylenediamine series reducing agent and phenolic or active methylene couplers is proposed in U.S. Pat. No. 3,531,286; p-aminophenol series reducing agents are proposed in U.S. Pat. No. 3,761,270; sulfonamidophenolic reducing agents are proposed in Belgian Pat. No. 802,519 and Research Disclosure, page 32, Sept. 31, 1975; and a combination of a sulfonamidophenolic reducing agent and 4-equivalent couplers is proposed in U.S. Pat. No. 4,021,240.
Also, regarding a process of forming positive color images by a light-sensitive silver dye bleaching process, useful dyes and bleaching processes are described, for example, in Research Disclosure, pages 30-32 (RD-14433), April, 1976, ibid., pages 14-15 (RD-15227), December, 1976, U.S. Pat. No. 4,235,957, etc.
Furthermore, image forming processes by heat development utilizing a compound which previously has a dye moiety and can release a mobile dye in porportion to or in counterproportion to the reduction reaction to the silver of the silver halide at a high temperature state is disclosed in European Patent Application (Laid Open) Nos. 76,492 and 79,056, Japanese Patent Application (OPI) Nos. 28928/83, 26008/83, etc. (the term "OPI" as used herein refers to a "published unexamined patent application open to public inspection").
Also, processes of transferring mobile dyes imagewise formed by heat development into an image receiving layer by heating and image receiving materials which are used for such processes are described in Japanese Patent Application (OPI) Nos. 58543/83 (corresponding to U.S. Pat. No. 4,500,626), 79247/83 (corresponding to U.S. Pat. No. 4,483,914), 168439/84 (corresponding to U.S. patent application Ser. No. 509,592, filed on Mar. 16, 1984), etc.
However, in such an image forming process having heatng step(s), the supply of necessary photographic reagent(s) from a developer, etc., cannot be expected and hence it is necessary that photographic reagents necessary for development are all previously incorporated into the light-sensitive materials. In this case, when the photographic reagents are incorporated into the light-sensitive materials in active form, the photographic reagents react with the other components in the photographic light-sensitive materials during the storage thereof before processing or are decomposed by the influences of heat, oxygen, etc., whereby the desired performance of the photographic reagent(s) cannot be obtained at processing.
One attempt at solving these problems involves incorporating a photographic reagent in a photographic light-sensitive material in a substantially inactive form, i.e., a precursor for the photographic reagent. When a useful photographic reagent is a dye, the spectral absorption of the dye is shifted to a short wavelength side or a long wavelength side by blocking the functional group of the dye, which gives large influences on the spectral absorption of the dye, whereby even when the dye coexists in a silver halide emulsion layer having a corresponding photosensitive spectral region, the reduction in sensitivity by a so-called filter effect does not occur. When a useful photographic reagent is an antifoggant or a development inhibitor, by blocking the active group thereof, the occurrence of desensitizing action by the adsorption of the photographic reagent onto light-sensitive silver halide or the formation of a silver salt during the storage of the light-sensitive material can be restrained and at the same time by releasing the photographic reagent at the desired time, the formation of fog can be reduced without reducing the sensitivity, the occurrence of superdevelopment fog can be inhibited, or the development can be stopped at the desired time. Also, when the useful photographic reagent is a developing agent, an auxiliary developing agent or a fogging agent, by blocking the active group or the adsorptive group, the occurrence of various photographic undesirable actions by the formation of semiquinone or oxidation products by air oxidation during the storage of the light-sensitive materials can be prevented or the formation of fogging nuclei during storage by injecting into silver halide can be prevented, which results in realizing stable processing. Furthermore, when the photographic reagent is a bleach accelerator or a blix (bleach-fix) accelerator, by blocking the active group thereof, the occurrence of the reaction with the other components contained therein during the storage of the light-sensitive material can be inhibited and by releasing the blocking group at processing, a desired performance of the reagent can be obtained at the desired time.
Various practical techniques for blocking photographic reagents are known in conventional photographic light-sensitive materials. For example, techniques utilizing a blocking group such as an acyl group, a sulfonyl group, etc., are described in Japanese Patent Publication No. 44805/72; techniques utilizing a blocking group releasing a photographic reagent by a so-called reverse Michael reaction are described in Japanese Patent Publication Nos. 17369/79, 9696/80 and 34927/80; techniques utilizing a blocking group releasing a photographic reagent with formation of quinonemethide or a quinonemethide-like compound by intramolecular electron transfer are described in Japanese Patent Publication No. 39727/79 and Japanese Patent Application (OPI) Nos. 135944/82, 135945/82 and 136640/82; techniques utilizing an intramolecular ring closing reaction are described in Japanese Patent Application (OPI) No. 53330/80; and techniques utilizing the cleavage of a 5-membered or 6-membered ring are described in Japanese Patent Application (OPI) Nos. 76541/82, 135949/82 and 179842/82.
However, these known techniques utilize hydrolysis or dehydrogenation by the action of OH.sup.- at wet development. Precursor techniques in the case of dry processing using an organic base have not yet been known.